Frictional coupling device for watch movement

ABSTRACT

A frictional coupling device for two rotating, coaxial components of a watch movement comprising an arbor, a pinion on that arbor which is freely engaged and which is provided with two gripping elements located on either side of the arbor, and a connecting member that is elastically deformable. The connecting member fits around the arbor and the two gripping elements of the pinion. The connecting member presses against the arbor and becomes frictionally interlocked with the arbor such that when the arbor rotates, the connecting member rotates and causes the encompassed pinion to also rotate.

United States Patent [1 1 [111 3,7 Zaugg Feb. 5, 1974;

[ FRICTIONAL COUPLING DEVICE FOR 3,406,583 10/1968 Baier 64/30 R x WATCH MOVEMENT 3,648,476 3/1972 Linstromberg 64/30 R X Inventor: Roland Zaugg, Grenchen,

Switzerland Assignee: A. Schild S.A., Grenchen (Canton of Soleure), Switzerland Filed: July 12, 1972 App]. No.: 271,131

Foreign Application Priority Data July 12, 1971. Switzerland 10225/71 US. Cl. 74/432, 64/30 R Int. Cl. F16h 55/00, Fl6d 7/02 Field of Search 74/432; 64/30 R References Cited UNITED STATES PATENTS 4/1968 Manoni 154/30 R Primary ExaminerLeonard H. Gerin Attorney, Agent, or Firm-Stevens, Davis, Miller & Mosher 5 ABSTRACT 8 Claims, 2 Drawing Figures Patented Feb. 5, 1974 FRICTIONAL COUPLING DEVICE FOR WATCH MOVEMENT The object of the present invention is a frictional coupling device located between two rotational and coaxial components of a watch movement.

Frictional couplings of this kind are found in conventional watch movements between the cannon-pinion supporting the minute hand and the arbor of the center wheel and pinion which pivots at the center of the bottom plate between the latter and the train-bar. The cannon-pinion is provided with a long bushing which is reamed with respect to the end of the arbor of the cen-. ter wheel-and-pinion, this end extending beyond the outer side of the bottom plate. This part of the arbor is provided with a groove or slot and coupling is achieved by tightening the bushing of the cannon-pinion against the arbor at two locations that are diametrically opposite.

This frictional coupling suffers from difficult execution and there is further great difficulty in achieving a frictional couple which is at all constant from one coupling device to the next within the same production serie's. Such a system or device does not allow for the guaranteed interchangeability of cannon-pinions and of center wheel-and-pinions. Each cannon-pinion must be specially or individually adapted to the wheel-andpinion on which it is mounted. It is clear that such an arrangement does appreciably complicate repairs and replacement of parts.

Classical couplings suffer from another drawback, namely they require much space height-wise. In certain watch movements, the center wheel-and-pinion is eccentric and the cannon-pinion drives a wheel or centerpinion which pivots about a fixed peg'located at the center of the bottom plate. In that case, the frictional coupling between cannon-pinion and wheel-andpinion arbor must be housed next to the inside of the bottom plate. Its dimensions in axial direction must be very small and further it must be of improved reliability since any correction would imply complete frame dismantling.

Frictional coupling devices of small size in the axial direction are already known, which comprise an elastic wire or thread folded into a triangle and on one hand pressing against the arbor and on the other against the hub coupled to that arbor. Such executions or embodiments sometimes are meant for horology components or pieces of average dimensions such as alarm clocks or alarms. They do not provide sufficient reliability for use in watch movements, particularly not in watch movements with eccentric center wheel-and-pinions.

In other instances, where the hub of the wheel to be connected to a rotating arbor by means of frictional coupling is made of plastic, an elastic wire or thread coiled in loops and surrounding the hub so as to press it against the arbor is being used. This kind of coupling is not suitable for wheel-and-pinions with metal hubs which are meant for watch movements.

In order to eliminate hand-wobble in movements where the minute hand is driven indirectly, the suggestion has been made that an elastic disc or plate blanked in the shape of a U be so emplaced as to engage a slit in the center-pinion bushing and press againstthe fixed peg around which this center-pinion is rotating, while the other arm of said elastic disc laterally presses against the center-pinion bushing. This known device or arrangement does not constitute a frictional coupling but merely a brake.-

The purpose of the present invention is to create a frictional coupling capable of reliably driving the cannon-pinion by means of the arbor of the center wheeland-pinion, for movement with the eccentric center wheel-and-pinion. The frictional device according to the invention will therefore offer high reliability without need for prior corrections and also will offer small size in the axial direction, while being simple, easy to manufacture and easy to assemble.

In order to achieve this goal, the device according to the invention is characterized as comprising a shaped, elastic component that grips or hooks onto one of said elements and that presses against a cylindrical surface of the other.

The attached drawing illustratively shows a mode of embodiment of the device according to the invention.

FIG. 1 is a view in axial section, and

FIG. 2 is a view of a section along line Il-II of FIG. 1.

The drawing shows an assembly with an eccentric center wheel 1, the arbor 2 which is made of one piece with a pinion 3 and supports the wheel of the center wheel-and-pinion 5 force-fitted against a shoulder 4. Arbor 2 at both ends is provided with journals 6 passing through the perforated jewels 7, one jewel being forcefitted into an opening of bottom plate 8 and the other into a corresponding opening, and of the same axis, in train-bar 9.

The arbor of the center wheel-and-pinion 1 supports a cannon-pinion 10 between bottom plate 8 and pinion 3; this cannon-pinion may for instance be connected to a center pinion bearing the minute hand by means of a countershaft. Cannon-pinion 10 comprises a hub extending in the axial sense on both sides of toothing 1 1. On one side this hub forms an annular rib 12 which is removed from arbor 2 because of a circular recess 13. On the other side, the hub 10 consists of two catches or holding parts 14 and 15 in the shape of diametrically opposite crown segments which are bounded by parallel flat sides 16 and 17. These two catches are made by turning on the lathe an annular hub of same inner diameter as the cannon-pinion reaming but of lesser width at the end of cannon-pinion 10, then by partly milling this annular section so as to leave only the two catches.

The reaming of cannon-pinion 10 is adapted to the diameter of arbor 2 so as to allow free rotation but without play between these two parts. Opposite catches l4 and 15, there is a circular groove 18 in arbor 2, the groove thus being in the immediate vicinity of upper journal or pivot 6.

The final element of the frictional coupling is a shaped, elastic component 19 consisting of a flat washer blanked for instance from a steel plate or sheet and with circular periphery and with a shaped central opening and radial slit.

As shown in FIG. 2, the central opening and the slit in component 19 roughly assume the shape of a cross, so that the inner edges of said opening and slit define two projections of triangular shape, 20 and 21, located opposite the slit, and two larger projections 22 and 23 located on either side of the slit and of which the ends are blanked as concave tips 24 and 25 with smooth radii. The dimensions of this elastic component are such that when the cannon-pinion l0 engaged arbor 2, the

washer.19 may engage the assembly thus constituted,

and by means of slight deformations, the concave ends 24 and 25 of projections 22 and 23 may engage groove 18 while the aligned flanks of projections 20 and 21 grip the sides 16 of catches 14 and 15. Axial connection between elements 1 and then is achieved on the one hand by rib 12 pushing against pinion 3 and on the other hand by projections 24 and 25 engaging into groove 18. Further, projections 24 and 25 rigidly connect the two rotating wheel-and-pinions by radially pressing against the inside of groove 18, as long as the couple being transmitted from one to the other does not exceed a given limiting value. Experiments have shown that the limiting couple resulting from the contact of the concave segments 24 and 25 against the inside of the groove 18 is of constant magnitude with acceptable tolerances even when manufactured from mating pieces of the coupling which themselves have fairly substantial tolerances.

Obviously the described device, in another embodiment, might be achieved between a conventional cannon-pinion provided with a bushing passing through the dial central opening on one hand, and the arbor of a center wheel-and-pinion located at the center of the movement.

In other embodiments, the shape and the location of catches 14 and 15, also the shape of the elastic component connecting the two coupling elements may differ from those illustrated in the drawing.

The device described above offers multiple advantages. Firstly, it requires very little space in the axial direction.

Secondly, blanking of disc 19, lathe-turning and milling of catches 14 and 15 and lathe-turning of arbor 2 may be carried out in mass-production with conventional machinery and are of such accuracy or precision that without corrections a coupling will be obtained having a well defined couple limit, constant and relatively strong.

A third advantage is that the assembly of the device is very simple. Because of the symmetry in the shape of catches 14 and 15, and similarly for the disc or washer 19, it is possible to position the latter without paying attention as to how it is being fed in, and therefore assembly operations are appreciably facilitated while at the same time many assembly errors are eliminated.

Fourthly, because of the pressure of projections and 21 on the catches 14 and 15, the cannon-pinion is coupled to the arbor without there being play between them. Thus, when the hands have been set to the proper time, the minute hand will be immediately driven. This would not be the case if there were play in the coupling.

Finally, experience has shown that the described device remains insensitive to wear or remains unaffected by it. While of very small size, the disc or Washer 19 constitutes an elastic component with large capacity for deformation and ensures a fairly powerful driving couple without suffering permanent deformation.

What is claimed is:

l. A frictional coupling device for two rotating, coaxial components of a watch movement comprising an arbor, a pinion on that arbor which is freely engaged and which is provided with two gripping elements located on either side of the arbor, a groove in the arbor at the level of the gripping elements, and a connecting member that is elastically deformable and that presses against the groove in the arbor and against the gripping elements so as to be integral with the pinion when rotating and so as to exert a pressure on the arbor.

2. A device according to claim 1 wherein the gripping elements are made up of two diametrically opposite catches projecting from the pinion in the axial direction and bounded laterally by two concentric cylindrical surfaces and by two parallel planes.

3. A device according to claim 1 wherein the connecting member is made up of an annular disc or washer with a slit and of which the inner periphery defines four projections, two of these being located on either side of the slit and pushing against the arbor while the other two are gripped by said gripping elements.

4. A device according to claim 1 wherein the connecting member has two projections which press against the arbor in said groove and which interlock said connecting member with respect to the arbor in the axial direction.

5. A device according to claim 4 wherein said pinion is kept between the connecting member and a shoulder or lip of the arbor.

6. A device according to claim 3 wherein the two projections pressing against the arbor engage into said groove and interlock the connecting member with respect to the arbor in the axial direction.

7. A device according to claim 6 wherein said pinion is kept between the connecting member and a shoulder or lip of the arbor.

8. A device according to claim 1 wherein the arbor pivots at its two ends between the bottom plate and a movement bar or bridge, wherein it is interlocked to a pinion and to a wheel and wherein it constitutes an eccentric center wheel-and-pinion, said first pinion being provided with gripping elements constituting the movements cannon-pinion. 

1. A frictional coupling device for two rotating, coaxial components of a watch movement comprising an arbor, a pinion on that arbor which is freely engaged and which is provided with two gripping elements located on either side of the arbor, a groove in the arbor at the level of the gripping elements, and a connecting member that is elastically deformable and that presses against the groove in the arbor and against the gripping elements so as to be integral with the pinion when rotating and so as to exert a pressure on the arbor.
 2. A device according to claim 1 wherein the gripping elements are made up of two diametrically opposite catches projecting from the pinion in the axial direction and bounded laterally by two concentric cylindrical surfaces and by two parallel planes.
 3. A device according to claim 1 wherein the connecting member is made up of an annular disc or washer with a slit and of which the inner periphery defines four projections, two of these being located on either side of the slit and pushing against the arbor while the other two are gripped by said gripping elements.
 4. A device according to claim 1 wherein the connecting member has two projections which press against the arbor in said groove aNd which interlock said connecting member with respect to the arbor in the axial direction.
 5. A device according to claim 4 wherein said pinion is kept between the connecting member and a shoulder or lip of the arbor.
 6. A device according to claim 3 wherein the two projections pressing against the arbor engage into said groove and interlock the connecting member with respect to the arbor in the axial direction.
 7. A device according to claim 6 wherein said pinion is kept between the connecting member and a shoulder or lip of the arbor.
 8. A device according to claim 1 wherein the arbor pivots at its two ends between the bottom plate and a movement bar or bridge, wherein it is interlocked to a pinion and to a wheel and wherein it constitutes an eccentric center wheel-and-pinion, said first pinion being provided with gripping elements constituting the movement''s cannon-pinion. 